The present invention relates generally to the field of interconnects in integrated circuits, and more particularly to depositing and shaping liner materials for copper and other metal interconnects.
Integrated circuits transport signals between, among, into, and out of various circuit components and layers via interconnects. Interconnects are typically surrounded by one or more layers of liner material. Liner materials may be engineered or formed as an artefact of the deposition process. The liner material's electrical properties directly or indirectly affect the interconnect's overall resistance, which affects performance, as well as the interconnect's susceptibility to electromigration and time-dependent dielectric breakdown, which affect reliability.
Electromigration is the transport of material caused by the gradual movement of ions in the conductive interconnect due to the momentum transfer between conducting electrons and diffusing metal atoms. Excessive electromigration over time damages the interconnect, ultimately causing signal loss and failure of the circuit that depends on the interconnect.
Time-dependent dielectric breakdown is a result of long-time application of relatively low electric field, which can occur across dielectric layers between the interconnect and other circuit components. The breakdown is caused by the formation of a conducting path through the dielectric due to electron tunneling current.
As circuit components grow ever smaller and more densely placed, engineers and designers of integrated circuit interconnects continue to face challenges with performance and reliability of interconnects and the interconnect liners.